Histological tissue processing is an important part of many different medical and forensic situations. The processing is performed in order to create stained cellular structures on a microscope slide for subsequent study and analysis using a microscope. By way of example, a doctor may perform a biopsy, and remove a small sample of tissue from a patient. This tissue is then placed into a small container of preservative, i.e., a fixative. At the lab, a histotech removes the specimen from the fixative, and places it into a labeled cassette.
The specimen is now processed, either traditionally (i.e., without acceleration techniques such as the use of a microwave) or via microwave processing, to produce a stained version of the tissue.
In one example of microwave tissue processing, cassettes containing formalin-fixed tissue may be place into a rack, and the rack is then placed into a Pyrex™ dish of ethyl alcohol. This is the dehydration step. In a next step, “clearing”, isopropyl alcohol is applied to the tissue, which removes the remaining water, the ethyl alcohol, and fats from the tissue. In a next step, an embedding agent (e.g., Paraffin) is infiltrated and embedded into the tissue. Different agents may be used depending upon the protocol. For example, rather than use isopropyl alcohol, isoparaffinics may be used. In addition, the fixation of the tissue may be carried out by means other than with the use of formalin. For example, microwave-assisted fixation may be used with different agents such as a glyoxal fixative.
Other processing methods include, e.g., tissue processing for electron microscopy and heating or drying of slides containing specimens, to name just a few.